Evidence for increased NADPH-diaphorase-positive neurons in the central auditory system of the aged rat

Abstract

Conclusions: The age-related increase in the production of nitric oxide (NO) suggests that this increase was related to neuron aging. Additional studies may provide information regarding aging-related changes in the central auditory system. Objectives: Although NO has been associated with aging, it is unclear whether specific areas of the central auditory system are involved. We therefore assayed aging-related changes in NADPH-diaphorase (NADPH-d), a selective histochemical marker for NO, in the neurons of the central auditory system and other brain regions. Materials and methods: The numbers of NADPH-d-stained neurons and the area and staining density of cell bodies were examined in aged (24 months old) and younger (4 months old) Wistar rats. Results: The number of NADPH-d-positive neurons in the inferior colliculus was significantly increased in aged rats (p<0.05), whereas the area of NADPH-d-positive neurons in all areas did not differ significantly between aged and younger rats (p>0.05). The staining densities of NADPH-d-positive neurons in the inferior colliculus, the auditory cortex, and the visual cortex were significantly greater in aged compared with younger rats (p<0.05).

• Nicotinamide adenine dinucleotide phosphate
• aging
• auditory cortex
• cochlear nucleus
• inferior colliculus